During neap tides and between the 

 higher tides, water levels are generally 

 below the marsh. Dissolved organic matter 

 is probably absorbed and incorporated into 

 microbial and animal biomass. Both larvae 

 and adults of several marine invertebrates 

 are known to take up DOC rapidly (Manahan 

 1980), and even photosynthetic diatoms can 

 function as heterotrophs by taking up DOC 

 (Darley et al. 1979). 



4.5 SUMMARY OF CHAPTER 4 



The quality of food produced by 

 vascular plants and algae differs. Salt 

 marsh consumers, such as snails and crabs. 



can feed directly on algae and probably 

 assimilate a large proportion of the algal 

 organic matter which they ingest. 

 However, vascular plants are relatively 

 indigestible until they have been 

 partially decomposed by microbes. Then 

 the fungi and bacteria provide nutritious 

 food sources for snails, crabs, isopods, 

 and amphipods. Adding the decomposer step 

 to the food chain reduces the proportion 

 of plant productivity which can be 

 funneled to higher trophic levels. Hence, 

 in this conceptual model of southern 

 California salt marshes, algal mats take 

 on a food producer role which is greater 

 than that measurable by productivity or 

 biomass alone. 



56 



